/*------------------------------------------------------------------------*/
/*  Copyright 2014 Sandia Corporation.                                    */
/*  This software is released under the license detailed                  */
/*  in the file, LICENSE, which is located in the top-level Nalu          */
/*  directory structure                                                   */
/*------------------------------------------------------------------------*/


// nalu
#include <AssembleScalarElemDiffSolverAlgorithm.h>
#include <EquationSystem.h>
#include <SolverAlgorithm.h>

#include <FieldTypeDef.h>
#include <LinearSystem.h>
#include <Realm.h>
#include <SupplementalAlgorithm.h>
#include <TimeIntegrator.h>
#include <master_element/MasterElement.h>

// stk_mesh/base/fem
#include <stk_mesh/base/BulkData.hpp>
#include <stk_mesh/base/Field.hpp>
#include <stk_mesh/base/GetBuckets.hpp>
#include <stk_mesh/base/MetaData.hpp>
#include <stk_mesh/base/Part.hpp>

namespace sierra{
namespace nalu{


//==========================================================================
// Class Definition
//==========================================================================
// AssembleScalarElemDiffSolverAlgorithm - add LHS/RHS for scalar diff
//==========================================================================
//--------------------------------------------------------------------------
//-------- constructor -----------------------------------------------------
//--------------------------------------------------------------------------
AssembleScalarElemDiffSolverAlgorithm::AssembleScalarElemDiffSolverAlgorithm(
  Realm &realm,
  stk::mesh::Part *part,
  EquationSystem *eqSystem,
  ScalarFieldType *scalarQ,
  VectorFieldType *dqdx,
  ScalarFieldType *diffFluxCoeff)
  : SolverAlgorithm(realm, part, eqSystem),
    scalarQ_(scalarQ),
    diffFluxCoeff_(diffFluxCoeff),
    shiftedGradOp_(realm.get_shifted_grad_op(scalarQ_->name()))
{
  // save off fields
  stk::mesh::MetaData & meta_data = realm_.meta_data();
  coordinates_ = meta_data.get_field<VectorFieldType>(stk::topology::NODE_RANK, realm_.get_coordinates_name());
}

//--------------------------------------------------------------------------
//-------- initialize_connectivity -----------------------------------------
//--------------------------------------------------------------------------
void
AssembleScalarElemDiffSolverAlgorithm::initialize_connectivity()
{
  eqSystem_->linsys_->buildElemToNodeGraph(partVec_);
}

//--------------------------------------------------------------------------
//-------- execute ---------------------------------------------------------
//--------------------------------------------------------------------------
void
AssembleScalarElemDiffSolverAlgorithm::execute()
{

  stk::mesh::BulkData & bulk_data = realm_.bulk_data();
  stk::mesh::MetaData & meta_data = realm_.meta_data();

  const int nDim = meta_data.spatial_dimension();

  // space for LHS/RHS; nodesPerElem*nodesPerElem* and nodesPerElem
  std::vector<double> lhs;
  std::vector<double> rhs;
  std::vector<int> scratchIds;
  std::vector<double> scratchVals;
  std::vector<stk::mesh::Entity> connected_nodes;

  // supplemental algorithm setup
  const size_t supplementalAlgSize = supplementalAlg_.size();
  for ( size_t i = 0; i < supplementalAlgSize; ++i )
    supplementalAlg_[i]->setup();

  // deal with state
  ScalarFieldType &scalarQNp1   = scalarQ_->field_of_state(stk::mesh::StateNP1);

  // nodal fields to gather
  std::vector<double> ws_coordinates;
  std::vector<double> ws_scalarQNp1;
  std::vector<double> ws_diffFluxCoeff;

  // geometry related to populate
  std::vector<double> ws_scs_areav;
  std::vector<double> ws_dndx;
  std::vector<double> ws_deriv;
  std::vector<double> ws_det_j;
  std::vector<double> ws_shape_function;

  // define some common selectors
  stk::mesh::Selector s_locally_owned_union = meta_data.locally_owned_part()
    & stk::mesh::selectUnion(partVec_) 
    & !(realm_.get_inactive_selector());

  stk::mesh::BucketVector const& elem_buckets =
    realm_.get_buckets( stk::topology::ELEMENT_RANK, s_locally_owned_union );
  for ( stk::mesh::BucketVector::const_iterator ib = elem_buckets.begin();
        ib != elem_buckets.end() ; ++ib ) {
    stk::mesh::Bucket & b = **ib ;
    const stk::mesh::Bucket::size_type length   = b.size();

    // extract master element
    MasterElement *meSCS = sierra::nalu::MasterElementRepo::get_surface_master_element(b.topology());
    MasterElement *meSCV = sierra::nalu::MasterElementRepo::get_volume_master_element(b.topology());

    // extract master element specifics
    const int nodesPerElement = meSCS->nodesPerElement_;
    const int numScsIp = meSCS->numIntPoints_;
    const int *lrscv = meSCS->adjacentNodes();

    // resize some things; matrix related
    const int lhsSize = nodesPerElement*nodesPerElement;
    const int rhsSize = nodesPerElement;
    lhs.resize(lhsSize);
    rhs.resize(rhsSize);
    scratchIds.resize(rhsSize);
    scratchVals.resize(rhsSize);
    connected_nodes.resize(nodesPerElement);

    // algorithm related
    ws_coordinates.resize(nodesPerElement*nDim);
    ws_scalarQNp1.resize(nodesPerElement);
    ws_diffFluxCoeff.resize(nodesPerElement);
    ws_scs_areav.resize(numScsIp*nDim);
    ws_dndx.resize(nDim*numScsIp*nodesPerElement);
    ws_deriv.resize(nDim*numScsIp*nodesPerElement);
    ws_det_j.resize(numScsIp);
    ws_shape_function.resize(numScsIp*nodesPerElement);

    // pointer to lhs/rhs
    double *p_lhs = &lhs[0];
    double *p_rhs = &rhs[0];

    double *p_coordinates = &ws_coordinates[0];

    double *p_scalarQNp1 = &ws_scalarQNp1[0];
    double *p_diffFluxCoeff = &ws_diffFluxCoeff[0];
    double *p_scs_areav = &ws_scs_areav[0];
    double *p_dndx = &ws_dndx[0];
    double *p_shape_function = &ws_shape_function[0];

    // extract shape function
    meSCS->shape_fcn(&p_shape_function[0]);

    // resize possible supplemental element alg
    for ( size_t i = 0; i < supplementalAlgSize; ++i )
      supplementalAlg_[i]->elem_resize(meSCS, meSCV);
    
    for ( size_t k = 0 ; k < length ; ++k ) {

      // get elem
      stk::mesh::Entity elem = b[k];

      // zero lhs/rhs
      for ( int p = 0; p < lhsSize; ++p )
        p_lhs[p] = 0.0;
      for ( int p = 0; p < rhsSize; ++p )
        p_rhs[p] = 0.0;

      //===============================================
      // gather nodal data; this is how we do it now..
      //===============================================
      stk::mesh::Entity const * node_rels = bulk_data.begin_nodes(elem);
      int num_nodes = bulk_data.num_nodes(elem);

      // sanity check on num nodes
      ThrowAssert( num_nodes == nodesPerElement );

      for ( int ni = 0; ni < num_nodes; ++ni ) {
        stk::mesh::Entity node = node_rels[ni];

        // set connected nodes
        connected_nodes[ni] = node;

        // pointers to real data
        const double * coords = stk::mesh::field_data(*coordinates_, node );

        // gather scalars
        p_scalarQNp1[ni]    = *stk::mesh::field_data(scalarQNp1, node );
        p_diffFluxCoeff[ni] = *stk::mesh::field_data(*diffFluxCoeff_, node );

        // gather vectors
        const int niNdim = ni*nDim;
        for ( int i=0; i < nDim; ++i ) {
          p_coordinates[niNdim+i] = coords[i];
        }
      }

      // compute geometry
      double scs_error = 0.0;
      meSCS->determinant(1, &p_coordinates[0], &p_scs_areav[0], &scs_error);

      // compute dndx
      if ( shiftedGradOp_ )
        meSCS->shifted_grad_op(1, &ws_coordinates[0], &ws_dndx[0], &ws_deriv[0], &ws_det_j[0], &scs_error);
      else
        meSCS->grad_op(1, &ws_coordinates[0], &ws_dndx[0], &ws_deriv[0], &ws_det_j[0], &scs_error);

      for ( int ip = 0; ip < numScsIp; ++ip ) {

        // left and right nodes for this ip
        const int il = lrscv[2*ip];
        const int ir = lrscv[2*ip+1];

        // corresponding matrix rows
        const int rowL = il*nodesPerElement;
        const int rowR = ir*nodesPerElement;

        // save off ip values; offset to Shape Function
        double muIp = 0.0;
        const int offSetSF = ip*nodesPerElement;
        for ( int ic = 0; ic < nodesPerElement; ++ic ) {
          const double r = p_shape_function[offSetSF+ic];
          muIp += r*p_diffFluxCoeff[ic];
        }

        double qDiff = 0.0;
        for ( int ic = 0; ic < nodesPerElement; ++ic ) {

          // diffusion
          double lhsfacDiff = 0.0;
          const int offSetDnDx = nDim*nodesPerElement*ip + ic*nDim;
          for ( int j = 0; j < nDim; ++j ) {
            lhsfacDiff += -muIp*p_dndx[offSetDnDx+j]*p_scs_areav[ip*nDim+j];
          }

          qDiff += lhsfacDiff*p_scalarQNp1[ic];

          // lhs; il then ir
          p_lhs[rowL+ic] += lhsfacDiff;
          p_lhs[rowR+ic] -= lhsfacDiff;
        }

        // rhs; il then ir
        p_rhs[il] -= qDiff;
        p_rhs[ir] += qDiff;        
      }

      // call supplemental
      for ( size_t i = 0; i < supplementalAlgSize; ++i )
        supplementalAlg_[i]->elem_execute( &lhs[0], &rhs[0], elem, meSCS, meSCV);

      apply_coeff(connected_nodes, scratchIds, scratchVals, rhs, lhs, __FILE__);

    }
  }
}

} // namespace nalu
} // namespace Sierra
